| Galilean or Negative This eyepiece (also called a negative eyepiece) was created by Galileo Galilei in 1610. It suffers just about every known optical defect except that it does provide an upright image. It must placed outside the focal plane to work. Oddly enough, this design is still used a great deal in inexpensive opera glasses, lorgnettes, and children's "binoculars". |
| Positive This positive eyepiece (as such) was created by [John?] Hall about 1615. It sole redeeming feature is it got people interested in telescopes and led to ever better designs. About the only "telescopes" which use this design today are people expermenting with optical labs that can be bought from companies like Edmund's Scientific. |
| Huygens This eyepiece, created by Christian Huygens in 1703, is an inexpensive eyepiece, simply designed and constructed. It does not perform well below f/10, suffering various aberrations if used with faster telescopes. |
| Mittenzway The Moritz Mittenzway modification of the Huygens design appeared around 1865. It replaces the field plano convex lens with a meniscus lens. It extends the Huygens design down to about f/8. |
| Ramsden Jesse Ramsden created this eyepiece in 1782. It has very poor eye relief (your eye must be held very close to the lens), and suffers from both chromatic and spherical aberrations. However this design was free of coma and led to other much more sucessful designs, the Kellner and later the Plossl (and Super Plossls). It is extremely simple to make and is very inexpensive. It appears in a great many "department store specials". Frequently replacing a Ramsden eyepiece with a more modern design results in dramatic improvements in inexpensive telescopes. |
| Kellner Carl Kellner modified the basic Ramsden design to create this eyepiece in 1849. In many respects this can be considered the first "modern" eyepiece. The major change is the replacement of the eye lens with a achromatic cemented doublet. It has good eye relief. It is relatively free of all serious aberrations. It works well even with telescope systems as fast as f/6. Its chief drawback is a tendency to form "ghost" images Various improved versions are on the market today such as the Edmund's RKE series of moderately priced eyepieces. |
| Plossl Simon Plossl modified the Kellner design to create this eyepiece in 1860. This design has two achromatic doublets. It reduces aberrations even more than the Kellner and is able to be used with telescopes as fast as f/4. Plossls and Super Plossls remain work horses of many systems including our own Meade LX200 16" SCT. |
| Orthoscopic Ernst Karl Abbe created the orthoscopic eyepiece in 1880. The major design change was the introduction of a cemented triplet field lens. This design was assumed to be the very best until the twentieth century combining very good eye relief with good freedom from coma and various aberrations. Cost was moderate and these eyepieces continue to be popular until the present. For their time one of the most remarkable features of the orthoscopic design was a field of view from 30deg; to 50°. |
| Erfles and Konigs Heinrich Erfle created this design in 1917. Its great advantage was an extraordinarily wide field of view (typically 60° to 70°) over earlier eyepieces. It suffers some loss of image quality at the edges of its view. In the 1930s(?) Albert Konig extended this design to shorter focal lenths. |
| Ultrawides Designing optics has always been a tedious task. Opticians have long understood how to design an optical system from theory, but in practice, complex optics with many elements required far too much time to allow many alternative designs to be tried. Actually grinding the lenses and seeing if they behaved as expected was even more difficult. Running the calculations on computers was possible, but it required many hours of main frame time on a circa 1975 system to establish a lens. There did not seem to be any market for these improved eyepieces. Personal computers changed this market place in two dramatic ways. It created a whole generation of new computer designed telescopes (Questars, Celestrons and later Meades as well others). It also allowed the computer intensive ray tracing programs to be run economically. Suddenly it became practical to design 5, 6, 7 or even 8 element optical systems where the individual elements were no longer restricted to simple plano convex and plano concave units. Exotic combinations of glass were tried on the computers and coatings were simulated. From this has come a wide variety of new eyepieces with extraodinarily wide fields of view, excellent eye relief, freedom from undesirable side effects and managable costs (although none of these super eyepieces would be called cheap). I'll point out The Nagler family of eyepieces are expensive, complex and superlative in design and image quality. They were first created by Albert Nagler during the 1980sand have become the industry standard of excellence. Typically these eyepieces have 7 or 8 lenses of various shapes and formed from as many as 4 differing densities of glass. These eypieces work well at focal lenths as fast as f/4, and superbly at slower focal lenths. The worst drawback of Naglers (like other eyepieces with five or more elements) is that light is lost at each interface reducing contrast and brightness. |
| Monocentrics This eyepiece seems to have been created by Robert Tolles which would make it a 20th century creation. This eyepiece is a specialty eyepiece with an unsually narrow acceptable image. It is completely free from "ghosts" which plague other eyepieces when looking at extremely bright objects. As such it is very good for examining planets and for spliting close doubles.
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置顶卡
变色卡
千斤顶
显身卡
